For what reason do we choose to calibrate or estimate parameters in DSGE models ?
That is the choice of the modeler. For example, if you want to convey a theoretical point that should be widely applicable, you often simply pick plausible parameter values. If you want to consider a particular country/time period, you estimate the model. Similarly, if your model is non-standard and there is no good evidence on plausible parameter values, you have no other choice than estimation.
Thank you @jpfeifer
As I understand the calibration is used in ready and tried models.